1. Percent Composition & Empirical Formulas

2. Percent Composition
Divide the mass of each element by the molar mass of the compound and multiply by 100
Can be found from the formula OR experimental data

3. Potassium Chromate
Formula: K2CrO4
Potassium:
Chromium:
Oxygen:

4. Potassium Chromate

5. Experimental Data
A g sample of an unknown compound is extracted from the roots of a plant. Decomposition of the sample produces g of carbon, g of oxygen, and g of hydrogen. What is the percent composition of the compound?

6. Empirical Formula
The simplest whole number ratio of a compound

7. Empirical Formula Turn mass into moles for each element
Divide all mole amounts by the smallest one
Write the formula using the whole number mole amounts as subscripts

8. Practice Problem
Find the empirical formula for the compound in the experimental data above.

9. Step 1
Turn mass into moles for each element.

10. Step 2
Divide all mole amounts by smallest number

11. Step 3
Write the formula using the whole number mole amounts as subscripts.

12. Limiting Reactant Practice
Due TOMORROW!
Limting Reactant Lab – DUE TOMORROW

13. Warm-Up
Answer these questions on the back of your Warm-Up Sheet from before break. DO NOT write the prompts. DO show your work.
What is the mass (in grams) of exactly one water molecule?
What volume of CO2 gas is produced from burning 2804 g (1 gallon) of gasoline?
Equation: 2 C8H O2  16 CO H2O